When comparing Monkey X Pro vs Unreal Engine 4, the Slant community recommends Monkey X Pro for most people. In the question“What are the best 2D game engines for Android?”Monkey X Pro is ranked 8th while Unreal Engine 4 is ranked 15th. The most important reason people chose Monkey X Pro is:

Developers can make native calls directly from Monkey code. This allows access to any native functionality and platform-specific features.

Pros

Pro

Native code support

Developers can make native calls directly from Monkey code. This allows access to any native functionality and platform-specific features.

Pro

Uses a great, easy to learn language

Monkey X uses a custom programming language (called Monkey) for all its scripting needs. Monkey is rather easy to learn, it's object-oriented which will help most programmers with understanding it. It's also statically typed and uses a garbage collector, helping to avoid manual memory management.

Pro

Very rapid prototyping

Monkey compiles to HTML 5 so it is very easy to make a small change and quickly preview it in a web browser.

Pro

Not running in its own VM

Unlike other multi-platform engines (Unity3D, Corona, etc), Monkey-X games do not run explicitly in their own virtual machines. Your code is translated into the native languages of each target platform, and then compiled as a native executable. For some platforms "native" is still a VM, but there is no overhead compared to other apps on that platform.

Pro

Partly open-source

The entirety of the base-language itself is open source. Commercial modules such as Mojo for non-free platforms cost a one-time fee. Though Mojo is not free for all targets, the targets for these platforms are, meaning it is possible to implement other frameworks for these targets.

The Desktop (GLFW and C++ based) and HTML5 implementations of Mojo are currently free and open source.

The language's development is completely public, and is managed via GitHub.

Pro

Free development license, including source code

The engine, including full access to source code, is licensed to developers for 5% royalty on resulting revenue if it exceeds $3000 per quarter.

Pro

Voxel cone tracing is a similar algorithm to ray tracing, but uses thick rays instead of pixel thin rays to be able vastly decrease the amount of computational power needed.

Pro

A visual scripting system for non-coders enables quick prototyping

Blueprints are authoring tools designed for non programmers so designers and other team members can help tweak and prototype. UE4's Blueprint scripts resemble flowcharts where each box represents a function or value, with connections between them representing program flow. This provides a better at-a-glance indication of game logic than a simple list of events, and makes complex behaviors easier to accomplish and games a lot faster to prototype.

Pro

Developers have full control of the engine and source code

UE4 gives full access to the C++ source code allowing editing and upgrading anything in the system.

Pro

Lots of resources to learn from

Epic provides multiple official video tutorials, lots of free example projects and content, an extensive wiki and regular streams showing how to use latest features.

Pro

Powerful material/shader system

Allows a texture/material artist or VFX artist to create amazing effects from the ground up.

Pro

Spectacular lighting visuals

Pro

Active community

Forums have many active and friendly members that are quick to respond and help out. Even staff is very active on forums.

Pro

Cross-platform editor and export

This engine exports for a big range of platforms including Linux. The editor can be run on Windows, MacOS, and Linux (Early Access).

Pro

Fast compilation for quick iteration

Recompiling an entire game to test a small change takes up a lot of time. UE4 quickly compiles in seconds instead of minutes improving iteration time by an order of magnitude.

Pro

Quick release-cycle

New feature releases can be commonly expected about once a month.

Pro

AAA Ready

This is ready to make the next AAA game.

Pro

Professional feature set for all aspects of game development

Almost everything a game developer wants has a deep and sophisticated tool waiting for them in UE4. No external plugins are needed to make powerful materials, FX, terrain, cinematics, gameplay logic, AI, animation graphs, post process effects, lighting etc.

Pro

Realistic graphics

Pro

Proven track record

Pro

No coding experience needed

Cons

Con

The documentation is not very thorough

The documentation contains a reasonably detailed language overview, and a somewhat-generated list of the included modules, classes, and methods. Module descriptions are rather lax, but usually present. Method descriptions tend to be short, and a majority of them contain no usage snippets; most parameters have very minimal descriptions. And there are no community collaboration features to help improve it, besides GitHub.

Con

You'll have to learn a new programming language

Even though this is not a problem if you're new to programming (since you'll have to learn a language anyway), having to learn a new language develop games is a lot of friction for people that already know how to program in other languages.

Con

No real asset store

Untangling how to keep assets in the ".data" requires attention and a filenaming convention.

Con

Very high build size

A blank project will build in to a minimum of 200 MB.

Con

Slow

Compared to other engines, UE4 seems to perform various actions considerably slower. Actions like starting the engine, opening the editor, opening a project, rebuilding shaders, updating references, calculating lightmaps, saving projects, etc take long enough to get irritating and end up wasting precious development time.

Con

Extremely long build times

Making a full rebuild, including engine can take a good 30minutes. If you plan to use Unreal professionally, you better get some licenses for Incredibuild as well.

Con

No drawcall batching, performance is very bad on mobile

There's no dynamic batching support to minimize drawcalls. There's InstancedStaticmesh concept in UE4, but it's 3d only, functionally limited and requires hardware support which rules out most mobile devices.

Con

Royalty based

5% of profits will go to Unreal after $3000 earned in a quarter.

Con

C++ - oriented development cycle: slow turn-around times

The Unreal Editor is the main place to do stuff (of course), so if someone wants to do a lot of C++ stuff, the compilation and linking turn-around times can be painful. Still they probably are quite fast in comparison to the provided featureset.. Still ,they are far from optimal.

Con

Hard engine for beginners

This engine not easy for beginners

Con

Poor documentation

Most of the "documentation" for code is actually just automatically generated from the source. If you're interested in knowing how things are supposed to work, you must either go to their answers site or pay for UDN.

Often their examples won't even compile, since they were written for now outdated versions.

Con

Steep learning curve

Especially when compared to its primary competitor, Unity.

Con

They spend more time adding features than fixing existing ones

Con

C# not natively supported

UE4 does not support C# natively, but this can be achieved through MonoUE, although it requires using the MonoUE fork instead of UE itself.

Con

Poor quality assurance on their releases

After each release they almost immediately release a hotfix. And another one. And another one.

Con

Tutorials do not go in-depth enough

The blueprint tutorial just teaches how to turn on a light when you press f.

Con

Extremely poorly designed

The code is a mess.

Everything is connected, a single Actor is 1500 bytes, because it contains a million things that Epic once needed in a game.